From 81c07553e62efdc5de61f72b388878d50b8dbba9 Mon Sep 17 00:00:00 2001
From: Victor Timofei <victor@vtimothy.com>
Date: Tue, 3 May 2022 00:59:24 +0300
Subject: [PATCH] Add kprintf with decimal support

---
 kernel/kernel.c | 102 +++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 93 insertions(+), 9 deletions(-)

diff --git a/kernel/kernel.c b/kernel/kernel.c
index 374400a..110e3cf 100644
--- a/kernel/kernel.c
+++ b/kernel/kernel.c
@@ -1,6 +1,7 @@
 #include "multiboot.h"
 #include "psf.h"
 #include <stdint.h>
+#include <stdarg.h>
 
 #if defined (__linux__)
 #error "You are not using a cross-compiler, you will most certainly run into trouble"
@@ -22,6 +23,9 @@ multiboot_info_t *mbi;
 uint32_t console_y;
 uint32_t console_x;
 
+uint32_t console_max_y;
+uint32_t console_max_x;
+
 #define PIXEL uint32_t
 
 #define CONSOLE_BG 0
@@ -52,30 +56,110 @@ void putchar (uint16_t c, int32_t cx, int32_t cy, uint32_t fg, uint32_t bg)
 
 }
 
+void console_push()
+{
+  // TODO: implement console pushing
+}
+
+void console_puts(uint16_t ch)
+{
+  if (ch == '\n' || console_x > console_max_x) {
+    console_x = 0;
+    console_y++;
+    return;
+  }
+
+  if (console_y > console_max_y)
+    console_push();
+
+  putchar((uint16_t) ch, console_x, console_y, CONSOLE_FG, CONSOLE_BG);
+  console_x++;
+}
+
 void console_write(char *str)
 {
   for (int idx = 0; str[idx] != '\0'; idx++ ) {
-    if (str[idx] == '\n') {
-      console_x = 0;
-      console_y++;
-      continue;
-    }
-    putchar((uint16_t) str[idx], console_x, console_y, CONSOLE_FG, CONSOLE_BG);
-    console_x++;
+    console_puts(str[idx]);
   }
 }
 
-void console_init()
+void console_init(multiboot_info_t *mbi)
 {
+  psf_font_t *font = (psf_font_t *)&consolefonts_binary__start;
+
+  console_max_y = mbi->framebuffer_height / font->height - 1;
+  console_max_x = mbi->framebuffer_width / font->width - 1;
+
   console_x = 0;
   console_y = 0;
 }
 
+void convert(int num, int base, char *buf, int bufsize)
+{
+  int idx = 0;
+  buf[idx] = '\0';
+
+  do {
+    /* Avoid buffer overrun */
+    if (idx == bufsize - 1)
+      break;
+
+    buf[idx] = (num % base) + '0';
+    num /= base;
+    idx++;
+  } while(num != 0);
+
+  buf[idx] = '\0';
+
+  for (int i = 0; i < idx / 2; i++) {
+    int tmp = buf[i];
+    buf[i] = buf[idx-1];
+    buf[idx-1] = tmp;
+  }
+}
+
+void kprintf(char *format, ...)
+{
+  va_list arg;
+  va_start(arg, format);
+
+  char buffer[50];
+  int i;
+
+  for (int idx = 0; format[idx] != '\0'; idx++) {
+    while (format[idx] != '%') {
+      if (format[idx] == '\0')
+        break;
+
+      console_puts(format[idx]);
+      idx++;
+    }
+    idx++;
+    switch (format[idx]) {
+      case 'd':
+        i = va_arg(arg, int);
+        if (i < 0) {
+          i = -i;
+          console_puts('-');
+        }
+
+        convert(i, 10, buffer, 50);
+        console_write(buffer);
+        break;
+    }
+  }
+
+  va_end(arg);
+}
+
 void kernel_main (uint32_t multiboot_struct_addr)
 {
   mbi = (multiboot_info_t *)multiboot_struct_addr;
   fb = (char *)mbi->framebuffer_addr;
   scanline = mbi->framebuffer_pitch;
 
-  console_write("Hello World!");
+  console_init(mbi);
+  kprintf("Console width is %d\n", mbi->framebuffer_width);
+  // TODO: Test line wrapping
+  //console_write("Hello World! 1234567890 1234567890 1234567890 1234567890 1234567890 1234567890 1234567890 1234567890 1234567890 1234567890");
 }